1. Field of the Invention
This invention relates to a method for measuring deviation and an apparatus which uses such a method, in which accuracy of alignment is measured when patterns on masks, reticles or the like, are printed in a superposed state while being aligned, for example, by an exposure apparatus for producing semiconductor devices.
2. Description of the Related Art
In a so-called exposure transfer apparatus for producing semiconductor devices for exposing and transferring circuit patterns on a reticle onto a photosensitive member on a wafer using ultraviolet rays, X rays or the like, relative alignment between the reticle and the wafer is one of important factors for improving the performance of semiconductor devices. Particularly, in alignment in recent exposure apparatuses, for example, a submicron alignment accuracy is required for effecting large-scale integration of semiconductor devices.
In many aligning apparatuses, so-called alignment patterns for alignment are provided on a reticle and a wafer, and alignment between the reticle and the wafer is performed utilizing positional information obtained from the alignment patterns. Conventionally, for actually measuring and evaluating the performance of alignment of an apparatus assembled as an exposure apparatus, fine patterns formed on two reticles are aligned and printed in a superposed state on a wafer, and the amount of deviation between the patterns on the wafer is measured visually or by performing image processing.
The above-described visual measurement has problems in that, for example, (1) accuracy in the measurement varies since the measurement greatly depends on the experience and skill of the person who performs the measurement, (2) the measurement takes time and care since the measurement is not automatic, and (3) high accuracy in the measurement cannot be obtained.
The above-described measurement which uses image processing also has problems in that, for example, time is needed because the measurement entails the performing of a complicated procedure, and high accuracy in the measurement cannot be obtained.